adjust desugaring for async fn to correct drop order #64525

nikomatsakis · 2019-09-16T20:21:36Z

Old desugaring, given a user function body { $stmts; $expr }

{
    let $param_pattern0 = $raw_param0;
    ...
    let $param_patternN = $raw_paramN;
    $stmts;
    $expr
}

New desugaring:

{
    let $param_pattern0 = $raw_param0;
    ...
    let $param_patternN = $raw_paramN;
    drop-temps {
        $stmts;
        $expr
    }
}

The drop-temps is an internal bit of HIR that drops temporaries from the resulting expression, but it should be equivalent to return { $stmts; $expr }.

Fixes #64512
Fixes #64391

rust-highfive · 2019-09-16T20:21:40Z

r? @petrochenkov

(rust_highfive has picked a reviewer for you, use r? to override)

petrochenkov · 2019-09-16T20:35:30Z

r? @cramertj (I guess)

Old desugaring, given a user function body { $stmts; $expr } ``` { let $param_pattern0 = $raw_param0; ... let $param_patternN = $raw_paramN; $stmts; $expr } ``` New desugaring: ``` { let $param_pattern0 = $raw_param0; ... let $param_patternN = $raw_paramN; drop-temps { $stmts; $expr } } ``` The drop-temps is an internal bit of HIR that drops temporaries from the resulting expression, but it should be equivalent to `return { $stmts; $expr }`.

nikomatsakis · 2019-09-16T20:45:23Z

@cramertj is on vacation -- maybe @davidtwco feels up to reviewing this?

r? @davidtwco

If you don't, though, let me know and we'll find somebody else. =)

estebank · 2019-09-16T22:07:04Z

This looks correct to me. If no reviewer gets a chance to see it in a timely manner, r=me.

src/librustc/hir/lowering/item.rs

src/test/ui/async-await/drop-order/drop-order-for-temporary-in-tail-return-expr.rs

nikomatsakis · 2019-09-17T08:33:40Z

@bors p=1

Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

rust-highfive · 2019-09-17T09:07:28Z

The job mingw-check of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-09-17T08:54:16.4179301Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-09-17T08:54:16.4370554Z ##[command]git config gc.auto 0
2019-09-17T08:54:16.4422163Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-09-17T08:54:16.4481784Z ##[command]git config --get-all http.proxy
2019-09-17T08:54:16.4661926Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/64525/merge:refs/remotes/pull/64525/merge
---
2019-09-17T09:02:07.1232465Z     Checking syntax_ext v0.0.0 (/checkout/src/libsyntax_ext)
2019-09-17T09:02:17.2358966Z error[E0308]: mismatched types
2019-09-17T09:02:17.2360290Z     --> src/librustc/hir/lowering.rs:2714:9
2019-09-17T09:02:17.2360870Z      |
2019-09-17T09:02:17.2361334Z 2713 |     fn lower_block_expr(&mut self, b: &Block) -> P<hir::Expr> {
2019-09-17T09:02:17.2361887Z      |                                                  ------------ expected `hir::ptr::P<hir::Expr>` because of return type
2019-09-17T09:02:17.2362390Z 2714 |         self.expr_block(self.lower_block(b, false), ThinVec::new())
2019-09-17T09:02:17.2362941Z      |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `hir::ptr::P`, found struct `hir::Expr`
2019-09-17T09:02:17.2364324Z      = note: expected type `hir::ptr::P<hir::Expr>`
2019-09-17T09:02:17.2364834Z                 found type `hir::Expr`
2019-09-17T09:02:17.2365094Z 
2019-09-17T09:02:17.3800894Z error[E0308]: mismatched types
2019-09-17T09:02:17.3800894Z error[E0308]: mismatched types
2019-09-17T09:02:17.3801168Z   --> src/librustc/hir/lowering/expr.rs:93:21
2019-09-17T09:02:17.3801334Z    |
2019-09-17T09:02:17.3801595Z 93 |                     this.with_new_scopes(|this| this.lower_block_expr(block))
2019-09-17T09:02:17.3802292Z    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `hir::Expr`, found struct `hir::ptr::P`
2019-09-17T09:02:17.3802738Z    = note: expected type `hir::Expr`
2019-09-17T09:02:17.3802957Z               found type `hir::ptr::P<hir::Expr>`
2019-09-17T09:02:17.3802990Z 
2019-09-17T09:02:17.4770011Z error[E0308]: mismatched types
2019-09-17T09:02:17.4770011Z error[E0308]: mismatched types
2019-09-17T09:02:17.4770467Z    --> src/librustc/hir/lowering/expr.rs:309:45
2019-09-17T09:02:17.4770660Z     |
2019-09-17T09:02:17.4770882Z 309 |         let then_arm = self.arm(then_pat, P(then_expr));
2019-09-17T09:02:17.4771161Z     |                                             ^^^^^^^^^ expected struct `hir::Expr`, found struct `hir::ptr::P`
2019-09-17T09:02:17.4771546Z     = note: expected type `hir::Expr`
2019-09-17T09:02:17.4771765Z                found type `hir::ptr::P<hir::Expr>`
2019-09-17T09:02:17.4771797Z 
2019-09-17T09:02:17.5715279Z error[E0308]: mismatched types
2019-09-17T09:02:17.5715279Z error[E0308]: mismatched types
2019-09-17T09:02:17.5715684Z    --> src/librustc/hir/lowering/expr.rs:377:45
2019-09-17T09:02:17.5715912Z     |
2019-09-17T09:02:17.5716208Z 377 |         let then_arm = self.arm(then_pat, P(then_expr));
2019-09-17T09:02:17.5716729Z     |                                             ^^^^^^^^^ expected struct `hir::Expr`, found struct `hir::ptr::P`
2019-09-17T09:02:17.5717353Z     = note: expected type `hir::Expr`
2019-09-17T09:02:17.5717635Z                found type `hir::ptr::P<hir::Expr>`
2019-09-17T09:02:17.5717670Z 
2019-09-17T09:02:17.7278751Z error[E0061]: this function takes 1 parameter but 2 parameters were supplied
2019-09-17T09:02:17.7278751Z error[E0061]: this function takes 1 parameter but 2 parameters were supplied
2019-09-17T09:02:17.7279051Z     --> src/librustc/hir/lowering/item.rs:1074:46
2019-09-17T09:02:17.7279212Z      |
2019-09-17T09:02:17.7279469Z 1074 |         self.lower_fn_body(decl, |this| this.lower_block_expr(body, false))
2019-09-17T09:02:17.7280109Z      | 
2019-09-17T09:02:17.7280313Z     ::: src/librustc/hir/lowering.rs:2713:5
2019-09-17T09:02:17.7280474Z      |
2019-09-17T09:02:17.7280474Z      |
2019-09-17T09:02:17.7280711Z 2713 |     fn lower_block_expr(&mut self, b: &Block) -> P<hir::Expr> {
2019-09-17T09:02:17.7281011Z 
2019-09-17T09:02:17.7281208Z error[E0308]: mismatched types
2019-09-17T09:02:17.7281398Z     --> src/librustc/hir/lowering/item.rs:1074:41
2019-09-17T09:02:17.7281569Z      |
2019-09-17T09:02:17.7281569Z      |
2019-09-17T09:02:17.7281804Z 1074 |         self.lower_fn_body(decl, |this| this.lower_block_expr(body, false))
2019-09-17T09:02:17.7282130Z      |                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `hir::Expr`, found struct `hir::ptr::P`
2019-09-17T09:02:17.7282539Z      = note: expected type `hir::Expr`
2019-09-17T09:02:17.7282986Z                 found type `hir::ptr::P<hir::Expr>`
2019-09-17T09:02:17.7283020Z 
2019-09-17T09:02:17.8255493Z error[E0308]: mismatched types
2019-09-17T09:02:17.8255493Z error[E0308]: mismatched types
2019-09-17T09:02:17.8256583Z     --> src/librustc/hir/lowering/item.rs:1237:27
2019-09-17T09:02:17.8257079Z      |
2019-09-17T09:02:17.8258343Z 1237 |                         P(user_body),
2019-09-17T09:02:17.8258937Z      |                           ^^^^^^^^^ expected struct `hir::Expr`, found struct `hir::ptr::P`
2019-09-17T09:02:17.8259854Z      = note: expected type `hir::Expr`
2019-09-17T09:02:17.8260343Z                 found type `hir::ptr::P<hir::Expr>`
2019-09-17T09:02:17.8260543Z 
2019-09-17T09:02:30.6044370Z error: aborting due to 7 previous errors
---
2019-09-17T09:02:30.7929633Z == clock drift check ==
2019-09-17T09:02:30.7946076Z   local time: Tue Sep 17 09:02:30 UTC 2019
2019-09-17T09:02:30.9552375Z   network time: Tue, 17 Sep 2019 09:02:30 GMT
2019-09-17T09:02:30.9559748Z == end clock drift check ==
2019-09-17T09:02:31.7950353Z ##[error]Bash exited with code '1'.
2019-09-17T09:02:31.7993678Z ##[section]Starting: Checkout
2019-09-17T09:02:31.7995803Z ==============================================================================
2019-09-17T09:02:31.7995879Z Task         : Get sources
2019-09-17T09:02:31.7995928Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

davidtwco

LGTM! r=me when CI is passing.

DropTemps(...) looks like a function, this looks like wacko special stuff

davidtwco

Oh, just remembered, will the reference need updated with this change? rust-lang/reference#674 is still open from the initial change.

nikomatsakis · 2019-09-17T12:57:23Z

@bors r=davidtwco

bors · 2019-09-17T12:57:24Z

📌 Commit 2d8b10f has been approved by davidtwco

nikomatsakis · 2019-09-17T12:58:33Z

@davidtwco

Oh, just remembered, will the reference need updated with this change? rust-lang/reference#674 is still open from the initial change.

I was planning to take a look at the reference and decide what needed to be updated.

bors · 2019-09-17T18:23:36Z

⌛ Testing commit 2d8b10f with merge 7efe1c6...

… r=davidtwco adjust desugaring for async fn to correct drop order Old desugaring, given a user function body `{ $stmts; $expr }` ``` { let $param_pattern0 = $raw_param0; ... let $param_patternN = $raw_paramN; $stmts; $expr } ``` New desugaring: ``` { let $param_pattern0 = $raw_param0; ... let $param_patternN = $raw_paramN; drop-temps { $stmts; $expr } } ``` The drop-temps is an internal bit of HIR that drops temporaries from the resulting expression, but it should be equivalent to `return { $stmts; $expr }`. Fixes #64512 Fixes #64391

bors · 2019-09-17T22:21:04Z

☀️ Test successful - checks-azure
Approved by: davidtwco
Pushing 7efe1c6 to master...

add test for drop order of temporary in tail return expression

ab1a3f0

rust-highfive assigned petrochenkov Sep 16, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Sep 16, 2019

nikomatsakis force-pushed the issue-64512-drop-order-tail-temp branch from 6b2fa9e to edb1a6f Compare September 16, 2019 20:24

rust-highfive assigned cramertj and unassigned petrochenkov Sep 16, 2019

nikomatsakis added 2 commits September 16, 2019 16:44

add regression test for issue-64391

9ae1a66

nikomatsakis force-pushed the issue-64512-drop-order-tail-temp branch from edb1a6f to 00d1590 Compare September 16, 2019 20:44

rust-highfive assigned davidtwco and unassigned cramertj Sep 16, 2019

Centril reviewed Sep 16, 2019

View reviewed changes

apply nits from centril

123f129

Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

nikomatsakis force-pushed the issue-64512-drop-order-tail-temp branch from bbf0439 to 291fb31 Compare September 17, 2019 08:53

davidtwco approved these changes Sep 17, 2019

View reviewed changes

nikomatsakis added 3 commits September 17, 2019 05:10

introduce lower_block_expr convenience function, and use it

0a11e80

use drop-temps { .. } pseudo-notation

716b2bc

DropTemps(...) looks like a function, this looks like wacko special stuff

adjust larger comment to include the body

2d8b10f

nikomatsakis force-pushed the issue-64512-drop-order-tail-temp branch from 291fb31 to 2d8b10f Compare September 17, 2019 09:10

davidtwco reviewed Sep 17, 2019

View reviewed changes

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 17, 2019

bors added the merged-by-bors This PR was explicitly merged by bors. label Sep 17, 2019

bors merged commit 2d8b10f into rust-lang:master Sep 17, 2019

sfackler mentioned this pull request Sep 18, 2019

async functions fail to move values into generated futures in the latest nightly #64391

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adjust desugaring for async fn to correct drop order #64525

adjust desugaring for async fn to correct drop order #64525

nikomatsakis commented Sep 16, 2019

rust-highfive commented Sep 16, 2019

petrochenkov commented Sep 16, 2019

nikomatsakis commented Sep 16, 2019

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bors commented Sep 17, 2019

adjust desugaring for async fn to correct drop order #64525

adjust desugaring for async fn to correct drop order #64525

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